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Taxonomic challenge With a 'modest' increase in effort, scientists could feasibly describe most of the species on the planet by the end of the century, a new analysis suggests.

Biologist Nigel Stork, from Griffith University, and colleagues say that many in the scientific community are unduly pessimistic about the chances of describing species before they go extinct.

In the journal Science this week, the researchers estimate that there are between 2 and 8 million species on Earth at the moment, of which 1.5 million have already been named.

Earlier calculations had suggested there were up to 100 million species on the planet, but Stork and colleagues say that their lower estimates are more statistically sound.

Although the researchers say the planet is in the midst of a "human-caused mass extinction phase with many species committed to extinction," they also argue that the rate of extinction is also slower than has been proposed.

They estimate that about 0.01 to 1 per cent of species are going extinct each decade.

"I'm much more optimistic than many other people," says Stork. "We're not as far down the track of species going extinct as people thought 30 years ago."

However, it's possible that climate change could increase the rate of extinctions, says Stork.

"To date I don't think we have any good modelling of what might happen with species extinction and climate change," he says. "The other factor will be the synergies [between climate change] and other pressures."

Boost in taxonomists

Another source of optimism is a recent boom in the number of taxonomists working around the globe, say the authors. Recent decades have had two to three times as many taxonomists as before the 1960s.

"There's reason to be optimistic that taxonomy is in good hands," says Stork.

The higher number of taxonomists has translated into an increase in the number of species being discovered. Over the past decade, an average of 17,500 new species have been described each year, rising above 18,000 annually since 2006, the authors say.

"At this rate of description, if there are two million species on Earth then most will have been described by 2040 ... if description rates are increased to 20,000 species per year then 3.5 million will be described by 2100."

Most of those species will be found in tropical forests, Stork says, with a smaller number in the world's oceans.

The authors say that increasing the global taxonomic effort ten-fold would cost between $0.5 billion and $1 billion a year, resulting in the description of all species within 50 years.

"We believe that with modestly increased effort in taxonomy and conservation, most species could be discovered and protected from extinction," they conclude.